Characterization of a medium size Xe/TMA TPC instrumented with microbulk Micromegas, using low-energy γ-rays

• Published in: Journal of instrumentation 2014-04, Vol.9 (4), p.C04015-C04015
• Main Authors: Álvarez, V, Borges, F I G M, Cárcel, S, Castel, J, Cebrián, S, Cervera, A, Conde, C A N, Dafni, T, Dias, T H V T, Díaz, J, Egorov, M, Esteve, R, Evtoukhovitch, P, Fernandes, L M P, Ferrario, P, Ferreira, A L, Freitas, E D C, Gehman, V M, Gil, A, Goldschmidt, A, Gómez, H, Gómez-Cadenas, J J, González-Díaz, D, Gutiérrez, R M, Hauptman, J, Morata, J A Hernando, Herrera, D C, Iguaz, F J, Irastorza, I G, Jinete, M A, Labarga, L, Laing, A, Liubarsky, I, Lopes, J A M, Lorca, D, Losada, M, Luzón, G, Marí, A, Martín-Albo, J, Martínez, A, Martínez-Lema, G, Miller, T, Moiseenko, A, Monrabal, F, Monteiro, C M B, Mora, F J, Moutinho, L M, Vidal, J Muñoz, Luz, H Natal da, Navarro, G, Nebot-Guinot, M, Nygren, D, Oliveira, C A B, Palma, R, Pérez, J, Aparicio, J L Pérez, Renner, J, Ripoll, L, Rodríguez, A, Rodríguez, J, Santos, F P, Santos, J M F dos, Segui, L, Serra, L, Shuman, D, Simón, A, Sofka, C, Sorel, M, Toledo, J F, Tomás, A, Torrent, J, Tsamalaidze, Z, Vázquez, D, Veloso, J F C A, Villar, J A, Webb, R C, White, J T, Yahlali, N, Aznar, F, Calvet, D, Druillole, F, Ferrer-Ribas, E, García, J A, Giomataris, I, Gracia, J, Coguie, A Le, Mols, J P, Pons, P, Ruiz, E
• Format: Article
• Language: English
• Subjects: Charge; Detectors; Diffusion; Drift; Instrumentation; Low energy; Planes; Searching; Xenon
• ISSN: 1748-0221; 1748-0221
• DOI: 10.1088/1748-0221/9/04/C04015

NEXT-MM is a general-purpose high pressure (10 bar, ~251 active volume) Xenonbased TPC, read out in charge mode with an 0.8 cm x 0.8 cm-segmented 700 cm super(2) plane (1152 ch) of the latest microbulk-Micromegas technology. It has been recently commissioned at University of Zaragoza as part of the R&D of the NEXT 0v beta beta experiment, although the experiment's first stage is currently being built based on a SiPM/PMT-readout concept relying on electroluminescence. Around 2 million events were collected during the last months, stemming from the low energy yrays emitted by a super(241) Am source when interacting with the Xenon gas (E sub( gamma ) = 26, 30, 59.5 keV). The localized nature of such events around atmospheric pressure, the long drift times, as well as the possibility to determine their production time from the associated a particle in coincidence, allow the extraction of primordial properties of the TPC filling gas, namely the drift velocity, diffusion and attachment coefficients. In this work we focus on the little explored combination of Xe and trimethylamine (TMA) for which, in particular, such properties are largely unknown. This gas mixture offers potential advantages over pure Xenon when aimed at Rare Event Searches, mainly due to its Penning characteristics, wave-length shifting properties and reduced diffusion, and it is being actively investigated by our collaboration. The chamber is currently operated at 2.7 bar, as an intermediate step towards the envisaged 10 bar. We report here its performance as well as a first implementation of the calibration procedures that have allowed the extension of the previously reported energy resolution to the whole readout plane (10.6% FWHM[at] 30 keV).